On May 22, an FBI agent fatally shot Todashev while questioning him in his Florida apartment about his connection to Tamerlan Tsarnaev — the suspect who died in the aftermath of the Marathon bombing attack. According to news reports, two Massachusetts state troopers were on the case with the FBI.

Given the involvement of Massachusetts law enforcement, the American Civil Liberties Union asked Attorney General Martha Coakley to launch an independent investigation. The AG turned down the request. What happened in Florida was out of her jurisdiction, Coakley said. That was fine with Governor Deval Patrick.

Talk about curious.

When a state police sergeant released photos showing the capture of accused Marathon bomber Dzhokhar Tsarnaev, Patrick acknowledged that rules were broken and the matter was quickly investigated. But when two state troopers are involved in a shooting death that is connected to the Marathon bombing, Patrick has nothing to say and defers to Coakley.

There are conflicting accounts of what triggered the incident, whether Todashev was armed, and how many times he was shot. On FBI orders, an autopsy report has not been released.

The FBI is doing its usual self-investigation, which is likely to lead to its usual self-exoneration. According to The New York Times, FBI agents shot and killed about 70 subjects and wounded 80 others between 1993 and 2011. In each case, an investigation concluded that the shooting was justified.

In the Todashev case, the Russian native was being questioned by the FBI about Tamerlan Tsarnaev’s alleged participation in the murders of three Waltham men. Their bodies were discovered on Sept. 12, 2011. In the aftermath of the Marathon attack, there was speculation that the Waltham murders may have been an early expression of Tsarnaev’s radicalization; and, if law enforcement officials had linked him to the crime, they might have been able to intercept the Tsarnaev brothers and stop their deadly plan.

That’s one theory. But Todashev’s death effectively shuts the door on anything he knew that might have implicated Tsarnaev in the Waltham deaths or explained Tsarnaev’s state of mind.

Here’s another theory. Maybe the FBI didn’t want Todashev’s information to get out to the public. Maybe it would make the FBI and other law enforcement authorities look like they knew or should have known about the danger Tsarnaev posed to innocent people standing at the Marathon finish line.

If this sounds familiar, it should. It’s the exact scenario that allegedly allowed Whitey Bulger to carry out his deadly agenda, while corrupt FBI agents looked the other way.

Seen through that prism, this isn’t a question about the rights of a Russian national during questioning by the FBI. It’s not a question of whether Todashev was a bad guy. It’s a question about the rights of American citizens to know what really happened in that Orlando apartment and why.

What’s the protocol for such questioning? Was it followed? What role did the two Massachusetts state troopers play in the interrogation? Did either one fire a gun? If a state trooper fired his weapon, that is cause in itself for an internal investigation.

“When something goes wrong during an operation involving Massachusetts law enforcement officers, Massachusetts residents deserve a thorough and transparent investigation by Massachusetts officials,” wrote Carol Rose, executive director of the ACLU of Massachusetts, in her letter to Coakley.

So far, what happened before the Marathon bombing and after is as transparent as smoked glass. The mystery contributes to distrust and dark theories.

Sunlight dispels the darkness. Massachusetts should do its part to answer the questions about what happened to Ibragim Todashev and why.